A construction/transport/farm machine such as a wheel loader have a steering wheel to perform a steering operation when running with high speed on a public road or a work site. Also, in the work site such that repeating short distance driving and the steering operation, a lever like a joystick is provided to perform a steering operation efficiently by a simple operation.
Thus in the wheel loader capable of operating the steering operation by both of a steering wheel operation and a lever operation, the steering operation is performed unintentionally when a driver touches the lever accidentally during the steering wheel operation.
To address this problem, a control device is disclosed that performs prior the steering wheel operation when the steering wheel and the lever are operated simultaneously (For example: Patent literature 1).
In the control device disclosed in Patent literature 1, a sequence valve that is attached to a control valve for a lever operation is provided. Then, when the steering wheel operation is performed, the sequence valve is operated by hydraulic oil flowing in the control valve for the steering wheel operation and the supply of the hydraulic oil from the control valve for lever operation to a steering cylinder is stopped.